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For Formula 1 fans, McLaren is a household name, a pillar of the championship for decades. While many remember the difficulties encountered by the team in 2015 after reuniting with its long-time partner Honda, few know that McLaren revolutionized the sport in the early 1980s.
On Sunday, April 12, 1981, the Buenos Aires circuit saw Nelson Piquet claim the victory that would ultimately crown him champion, but another significant, more discreet event also took place: the Marlboro-McLaren MP4/1 made its racing debut as the first carbon fiber monocoque.
The 1981 season opened amid controversy. FISA refused to homologate the Lotus 88 with its innovative double chassis concept, while the Brabham BT49C caused a sensation by using hydropneumatic suspension that circumvented the 6 cm minimum height rule, maximizing ground effect and keeping the car glued to the track. At the time, the Brabham team was led by Bernie Ecclestone. McLaren's carbon fiber solution was quickly copied by all the teams in the Formula 1 circus. To understand why, just take a look at the evolution of chassis. The first cars were based on ladder-type steel chassis that would be laughable on today's road cars. In the mid-1950s, manufacturers switched to welded steel tubular chassis, and then aluminum alloys gradually became the norm. Initially, these were simple aluminum sheets bolted to the chassis, but by the early 1980s, they had been replaced by sandwich panels: a honeycomb core sandwiched between two thin layers of aluminum. These panels were light and rigid, but flat, difficult to bend, and impossible to weld. They were therefore usually glued and riveted using aluminum supports. When McLaren introduced carbon fiber skins in April 1981, the flexibility of this material made it possible to mold the entire chassis into a single, truly monocoque structure. A composite material consists of two parts: a reinforcing fiber and a matrix that binds the fibers together and distributes the loads. The best-known fibers are glass, aramid (Kevlar), and carbon; there are others, such as Zylon, basalt, ceramics, and even plant fibers, although the latter have never found their place in composites used in motorsports. Carbon fiber itself is derived from PAN (polyacrylonitrile), a polymer also known in the textile world as Dralon. The process involves three stages: oxidation at around 250°C, carbonization in an oxygen-free atmosphere at 1,000-1,500°C, and finally graphitization at over 2,000°C. By adjusting the temperature and dwell time, manufacturers can adapt the stiffness and tensile strength of the fiber. The filaments obtained are grouped into strands of 1,000, 3,000, or 12,000 filaments, which are then woven or layered to form fabrics.
The matrix is most often a synthetic resin (polyester, epoxy, phenolic, or acrylic), although metal matrices (e.g., boron fiber-reinforced aluminum) and ceramic matrices have also been tested, the latter now being banned in F1. Carbon matrix composites are still used for brake discs and pads. Resins are generally two-component systems that cure when mixed, under the effect of heat or ultraviolet rays. In Formula 1, epoxy is the most commonly used material, offering excellent mechanical strength; phenolic resin is reserved for components that must withstand temperatures above 150°C. Carbon-epoxy composites are produced by “contact” molding: layers of carbon fabric impregnated with liquid resin are placed in a pretreated mold and then cured—either at room temperature for a day or in an oven heated to less than an hour. This simple method requires minimal equipment and can be implemented in a modest workshop. There is also a technique called “vacuum molding.” Its basic principle is similar to that of contact molding, but after the last layer of fabric is placed, a release film and a drainage felt are added, and then the whole assembly is sealed in a plastic bag from which the air is evacuated using a pump. The vacuum inside the bag, combined with atmospheric pressure, creates uniform pressure across the entire part, improving the compaction of the carbon layers and reducing the amount of resin needed to achieve a high-performance composite. The equipment required is minimal, but mastering the process is more demanding than for contact molding. Infusion works on a completely different principle. Layers of dry fabric are placed in the mold, wrapped in the same bag as for bag molding, and the air inside is evacuated using a pump. The liquid resin is contained in a tank connected to the bag by one or more pipes controlled by valves. When the valves open, the vacuum draws the resin into the bag, where it impregnates the fabric. Although complex and difficult to implement, this method is preferred for large components such as wind turbine blades.
In the “prepreg” method, the fabrics are already saturated with a highly viscous resin and are stored frozen. Once removed from the freezer, the resin begins to harden very slowly, giving the material a consistency similar to a thin sheet of leather that can be easily cut. The fabric layers are then arranged in the required order and orientation, placed in the same bag, and cured in an autoclave. The high pressure inside the autoclave compensates for the viscosity of the resin, ensuring adequate compaction. This is the technique used in Formula 1 and aerospace, as it is highly reproducible. Paradoxically, it requires the least manual skill, but remains the most expensive. Less common processes include filament winding for tubes or gas cylinders and injection molding.
Carbon/carbon composites When both the reinforcement and the matrix are made of carbon, the result is a carbon-carbon composite. In Formula 1, this material is mainly used for brake discs. The carbon fibers are knitted or woven in three dimensions to approximate the final shape, then impregnated with pitch (a petroleum distillation residue similar to bitumen). The part undergoes the same series of transformations as PAN-based carbon, including carbonization at approximately 2,200°F in an inert nitrogen atmosphere. Once the surface crust has been removed, the impregnation-carbonization cycle is repeated until the desired homogeneity is achieved. The component is then impregnated with liquid silicon to reinforce its abrasion resistance, then graphitized at temperatures above 2,000°C. Once cooled, it is machined to its final dimensions. The sandwich concept When talking about composites, the sandwich principle inevitably comes up: a lightweight, incompressible core is placed between two composite skins. In Formula 1, the most common core is Nomex honeycomb (phenolic resin-impregnated paper), which has been used alongside aluminum honeycomb since the 1980s. A lesser-known core, used in the floor of Chevrolet Corvettes, is balsa wood. Yes, wood can be part of a high-tech construction. As stiffness increases with the square of the thickness, a threefold increase in thickness results in a 27-fold increase in stiffness, making the additional weight of the core negligible compared to the gain in stiffness.
Beyond its low density, carbon fiber offers excellent tensile and compressive strength, as well as high stiffness. A carbon fiber part can be four times stiffer than an aluminum alloy part or ten times stiffer than a steel part of the same weight. Composite design allows engineers to align the fibers directly with the stresses a part will be subjected to, choosing the type of fiber, fabric, and orientation to optimize performance. This tailor-made approach eliminates material waste, unlike metals, which, with the exception of processes such as forging, offer the same strength in all directions. Developments The range of matrices and reinforcements used in composites has changed little over the years, but recent advances have opened up many new uses for these materials.
One area where progress has been made is in production: advances in rapid prototyping and tooling now make it possible to manufacture a completely new composite component in just three days, including molds. In addition, a range of 3D printing technologies allows manufacturers to work directly with graphite powder or long carbon fibers without the need for a traditional mold.
At the same time, this field covers extremes, from carbon nanotubes measuring just a few microns to the massive, wide-winged fibers that adorn the hoods of today's single-seaters. Take the Marlboro-McLaren MP4/1, for example. In 1981, all the cars in the championship were still equipped with bodywork on their chassis. The MP4/1, powered by a 3-liter Ford Cosworth V8 engine, was no exception to the rule, but its revolutionary carbon fiber shell was molded around a male punch-shaped mold. The bare shell, visible in the photo below, had surface defects that made it unsuitable for bodywork at that stage. It would be several years before the complete integration of shock absorbers and other suspension parts allowed the shell to also serve as the car's outer skin. History records that on Saturday, April 11, 1981, John Watson qualified in 11th position, well ahead of his teammate Andrea de Cesaris, who was still using the old chassis. The next day, Watson retired halfway through the race due to severe vibrations. However, on July 18 of the same year, he won the British Grand Prix at Silverstone, marking the beginning of carbon fiber's dominance in Formula 1. Content written by Patrice Véronel, distributed by FranceF1.
